Yeah, the only way to get more comfortable with it is to use it more, haha. But it'll come with time.
Some of the lighting on your more recent pictures looks a bit inconsistent. Have you tried doing a planes study to get more comfortable with your shapes?

The planes of the face are, well, planes on a face! They tell you where the lights and shadows fall and help you map out the likeness. The Asaro head is a good place to get started.
Note that these are a base to get you going. Modifying the planes is how you get different likenesses (pushing, pulling, stretching, etc), but memorizing the basic planes is a good idea.
Do a couple studies off of these, and when you feel more familiar with them, try to come up with different lighting and stretch or pinch the planes to see what you get.
Good luck.